This two-part, phase-I/II open-label multicenter trial will evaluate the safety and tolerance of two drug regimens in HIV-1-infected infants and children. In Part A, a triple-drug regimen (zidovudine plus lamivudine plus nevirapine) will be given to two cohorts of patients: 1) & 15 days and & 3 months and 2) > 3 months and & 2 years. In Part B, a quadruple-drug regimen (zidovudine plus lamivudine plus nevirapine plus 1592U89) will also be given to two cohorts of patients: 1) & 30 days and & 3 months and 2) > 3 months and & 2 years. Safety, antiretroviral activity and durability of viral suppression will be assessed. This study should provide some initial insight into the important question of whether early (< 90 days of age) potent antiretroviral combination therapy will provide long-term control of viral replication and prevention of immunodeficiency.